Utilizing a transplantable hamster insulinoma which is a homogeneous source of insulin producing cells, biochemical characterization of the mechanism by which glucagon stimulates insulin secretion and the role of calcium in secretion, are being conducted. Subcellular components and putative transport protein are being examined for their ability to regulate calcium handling with the goal of dissecting the mechanism of glucose induced calcium fluxes. The Cyclic AMP activation of protein kinase is being studied to determine the critical substrates for protein kinase action in secretion and, more generally, to examine the relationship of the various forms of Cyclic AMP-dependent protein kinase in different tissues and different intracellular sites.